1. Field of the Invention
The present invention relates to an ink composition for writing instrument which can write on various writing surfaces such as a resin surface, a glass surface, a metal surface, etc., is excellent in a line sticking property to non-absorption surfaces, a water resistance and an alcohol resistance which can certainly write on said surfaces even if these writing surfaces have a releasing property and a water repellency, and which is useful as, for example, marking pens, sign pens and ball point pens.
2. Description of the Prior Art
Inks used for conventional oil base sign pens and the like contain xylene, cellosolve and ketones as principal solvents, and therefore an adverse effect to a human body is concerned. Further, there is a problem that they have an inferior alcohol resistance and the drawn lines thereof are erased with an alcohol in a certain case.
Inks using alcohols such as ethanol as a principal solvent have a problem that they have no fastness and a low sticking property against a non-absorbing surface, and further have a problem that they have a poor alcohol resistance and the drawn lines thereof are easily erased with alcohol. In addition, they have the restriction as well that they can not write on writing surfaces such as a resin surface, a glass surface and a metal surface.
On the other hand, an ink composition comprising a) a resin selected from the group consisting of an alkylphenol resin, a phenol-modified xylene resin and a phenol-terpene resin all of which are soluble in aliphatic hydrocarbon and/or alicyclic hydrocarbon solvents, b) a medium viscosity and/or high viscosity silicone oil which is soluble in aliphatic hydrocarbon and/or alicyclic hydrocarbon solvents and which is non-volatile and has a viscosity of 100 to 1,000,000 cs at 25.degree. C., c) a pigment and/or an oil soluble dye, d) an aliphatic hydrocarbon and/or alicyclic hydrocarbon solvent and e) a low viscosity silicone oil having a boiling point of 80 to 160.degree. C. and a viscosity of 1.5 cs or less at 25.degree. C. is disclosed in Japanese Patent Publication No. Hei 5-62630 as an ink composition which can write on water-repellent materials such as adhesive tapes, paraffin paper, released paper and the like and provides a good leveling property even when writing on non-osmotic surfaces such as plastics, ceramics and metals.
Further, an oil base ink prepared by adding only a silicone base adhesive comprising a resin component and an oil or a gum component as film-forming resins to a colorant and a solvent is disclosed in Japanese Patent Publication No. Hei 7-91502 as an oil base ink composition which has an excellent adhesion against surfaces of materials having a low surface tension and a bad wetting property such as a kraft tape for packaging.
The ink compositions for writing instruments disclosed in these publications can write on water-repellent materials such as adhesive tapes, paraffin paper and released paper having a bad wetting property as compared with conventional ink compositions for writing instruments and provide good leveling properties even when writing on non-osmotic surfaces such as plastics, ceramics and metals. However, there are problems that the drawn lines are not yet sufficiently high in a drying property and a sticking property and are easily erased with solvents such as alcohol.
In particular, when important documents are written therewith, there is a concern that matters written with existing ink compositions for writing instruments might be altered, and therefore ink compositions for writing instruments providing drawn lines which are not erased with solvents and are not altered are desired.
On the other hand, a marking ink composition prepared by adding a mixture of a reactive linear silicone polymer and a branched silicone polymer to a marking ink is disclosed in Japanese Patent Publication No. Sho 62-16233 as a marking ink composition for marking on surfaces of various molded articles containing silicone or fluorinated resins.
Further, an oil base ink comprising a colorant, a synthetic resin, a fluorinated surfactant, a silane coupling agent and a solvent is disclosed in Japanese Patent Publication No. Sho 62-61239 as an oil base ink having a good adhesion even on a surface of a material having a markedly low surface tension and an inferior wetting property without showing a cissing phenomenon.
However, in the case of the marking ink composition disclosed in former Japanese Patent Publication No. Sho 62-16233 described above, marking is provided on surfaces of various molded articles containing fluorinated resins, and then the marking parts are cured by heating. Thus, it has a different use as an ink for writing instruments from that of the present invention and is different as well in a technical idea from the present invention.
Further, the oil base ink disclosed in latter Japanese Patent Publication No. Sho 62-61239 described above is similar to the ink composition of the present invention in terms of using fluorinated surfactants, but the above oil base ink is intended for making it possible to write on materials such as a gum tape for packaging which is covered on a surface thereof with a silicone coat without showing a cissing phenomenon, and therefore, there are problems that the drawn lines are not yet sufficiently high in a drying property and a sticking property and are easily erased with solvents such as alcohol. In particular, when important documents are written therewith, there is a concern that matters written therewith might be altered. Further, a synthetic resin and a solvent blended in this oil base ink have so far been used for conventional inks for writing instruments and are different in a use purpose and physical properties from the resin and the organic solvent used in the present invention. Thus, the above oil base ink has a different technical idea from that of the present invention from the viewpoint of the resin and the organic solvent.